Wired local area and wide area networks have become widespread and offer the ability to interconnect computers and other devices together thus permitting the sharing of data and other resources between machines. Wired networks offer significant advantages over conventional mechanisms for delivering and sharing all types of data, including non-real time data, e.g., data for which the timing of delivery is not critical, and real time data, e.g., data for which the timing of delivery is critical. Such non-real time data may comprise data processing data packets, such as database queries, static Internet content, electronic mail messages, and the like. The aforementioned real time data may comprise, for example, voice data (e.g., streaming voice data communicated as voice over Internet protocol (VoIP), video data and other data that is converted to corresponding signals which users perceive as a continuous stream (e.g., streaming multimedia content), and the like.
Wireless local area networks (WLANs) have recently become available as an alternative to wired local area networks. WLANs offer the same advantages of wired networks generally at a lower cost because less physical infrastructure and labor is required to install a WLAN. With a WLAN, wires are replaced with wireless links between an access point (AP) and wireless devices. Wireless devices may include desktop computers, portable computers, personal digital assistants (PDAs), printers, servers, and/or other devices that exchange data via wireless links.
An access point typically transmits and receives data to and from a wireless device within a coverage area. The coverage area typically corresponds to the inside of an office, house or other area of operation. Each wireless device may exchange data with the access point while in the coverage area and contends for the bandwidth provided by the access point with other wireless devices in the coverage area.
Data exchanged within WLANs generally is transmitted via radio frequency (RF) signals or optical signals. Wireless network connectivity differs from wired networks in that the transmission medium is subject to interference, high error rates and other factors that may limit or change bandwidth and/or data throughput.
With the exception of physical transmission differences, a WLAN typically employs a software and hardware architecture that is analogous to a wired network. WLANs, for example, commonly use the well-known OSI reference model which defines a communications protocol “stack.” WLANs also generally use a media access control (MAC) layer as part of this stack. The MAC layer may be responsible, for example, for controlling access to the WLAN by wireless devices. However, there are generally several differences between the MAC layer of a wired and wireless network.
Various MAC approaches for WLANs have been proposed. These approaches generally use polling techniques to find an available transmission channel and then transmit on the first available channel. The channels may include different frequency channels or portions of one or more different frequency channels pursuant to a code or time division multiple access scheme. As to any particular channel, the IEEE 802.11 media access control standard proposes a random access technique which uses a carrier sense with collision avoidance (CSMA/CA) scheme. This scheme is also widely implemented in wired networks. Pursuant to CSMA/CA, a device waits until no other device is transmitting on a chosen channel and then transmits data. If a collision occurs, the transmitting device backs off a random interval of time and begins again if the channel is clear. Pursuant to this technique, individual wireless devices eventually get access to the channel that the device is trying to access. However, this technique does not ensure an optimum allocation of wireless devices and/or data transmission among available channels.
Polling techniques have also been used to control access to wireless communications channels. Using polling techniques, wireless devices wait until they are polled by a master in order to transmit data. Polling techniques may be more successful at allocating devices to available communications channels. However, polling techniques generally require that a new MAC layer be provided in wireless devices. This requires deploying specially adapted hardware and/or replacing hardware within wireless devices. Moreover, such polling techniques and sequences typically are not efficient in allocating bandwidth among many devices with randomly and rapidly changing bandwidth needs.
In the case of multi-cast packet transmissions, such as those identified in the IEEE 802.11 standard, the sender sends one copy of content to multiple devices over the network. This keeps the sender from clogging or loading the network with duplicative packet content. However, multi-cast packets are sent without acknowledgement. Due to the bit error rate of a wireless medium and/or collisions from other multi-cast or uni-cast traffic, many multi-cast packets may not be received properly. Also, many multi-cast schemes such as the one identified in the IEEE 802.11 standard do not provide for packet acknowledgement at the receiver. Therefore, packets not properly received by a device are generally lost for that device. Therefore, multi-cast packet traffic is more susceptible degrading channel interference due to collisions and bit error rate than other types of packet transmission.
U.S. Pat. Nos. 6,049,549 to Ganz, et al., 5,751,708 to Eng, et al., and 6,393,261 to Lewis disclose technology relevant to wireless communication. The reader is directed to the disclosures of these patent documents for a better understanding of prior attempts at addressing the needs of wireless communication systems.
There is a need in the art for an efficient technique for managing bandwidth in a WLAN, such as a bandwidth management technique that does not require changing the MAC layer of wireless devices within the WLAN. There is a further need in the art for a technique for efficiently allocating wireless channels within a WLAN, such as a channel allocation technique that allows channels to be assigned efficiently to requesting wireless devices that takes account of quality of service requirements of each wireless device. There is still a further need in the art for a technique that implements intelligence to manage all available channels, such as to coordinate communications across the channels, such as an intelligent channel management technique that takes advantage of the existing MAC layer protocols to ensure that wireless devices within the WLAN are allocated efficiently among the available channels.